3 Answers
3

Make sure the exterior of your nozzle is clean. I've had bits of plastic pull at the extruding filament and change it's direction.

Attempt a "cold pull" or "atomic pull". On my Replicator 2 I do this by removing the extruder motor, heating up the hot end, manually pushing a length of filament through the nozzle, letting it cool slightly and tugging the filament (and hopefully the clog) out of the nozzle.

If you're extruding into the air, it's actually quite normal for the filament to come out in seemingly random directions. This shouldn't cause problems because the filament should always be getting squished onto the bed/layer underneath (or during bridging, getting stretched). The way the filament comes out in free air doesn't reflect how it behaves during printing.

If you are experiencing troubles then perhaps the nozzle is clogged with a small piece of debris (or, unlikely) the nozzle is actually damaged. There's little you can do to prevent that apart from using high quality filament and being careful not to damage the nozzle.

You very likely have partial clog in your hotend (the side which is clogged is the angle the extruding filament bends to) or have some plastic somehow stuck on the nozzle surface which the extruding plastic almost sticks to, like two droplets of water merging into one.

If its the latter, clean the hotend. It's easier to remove the plastic on it while its hot and soft, but don't burn yourself.

If it's a clog, that's more complicated.
First, you can make sure if it is indeed a clog or not by extruding into the air and measuring the wire with a caliper.
If it's thinner than it should be and your slicer settings are fine, then its a clog.

Ways to get rid of clog:

1) Replace the nozzle with a new one.

2) Break the clog with a sharp wire.

3) Take the hotend off and clean the nozzle with acetone ("acetone bath").

4) Blow torch on a removed nozzle. Dangerous thing to do for some but it works. If you're not confident or experienced to do this and the previous two solutions don't help, then go with option 1.